A combination of both ;) For large sites, with complicated navigation trees, I use a top horizontal navigation for the major categories ... and then a vertical sub-navigation for all of the category-specific links.

For functionality and space economy, I like the top horizontal, but for more artistic freedom, I'd go with left vertical. I don't like sites that try to put navigation on the right... Just not used to looking over there :-D.

For functionality and space economy, I like the top horizontal, but for more artistic freedom, I'd go with left vertical. I don't like sites that try to put navigation on the right... Just not used to looking over there :-D.

Regardless, I think it's pretty standard that if you need a dual navigation, either you do a two row horizontal with row 1 being main and row 2 being sub, or you do a combo with horizontal being main and vertical being sub. :)

Regardless, I think it's pretty standard that if you need a dual navigation, either you do a two row horizontal with row 1 being main and row 2 being sub, or you do a combo with horizontal being main and vertical being sub. :)